Furthermore the invention relates to a knee joint prosthesis executed with such a tibia platform as well as a closure plug for such a tibia platform.
A tibia platform of the type named which is known from FR-A-2 653 992 contains a metallic anchoring part and a joint support of polyethylene which can be inserted into this anchoring part. The anchoring part is executed with projections which can be introduced into the tibia bone in the form of a central pin and two ring shaped protrusions, the latter each containing a passage opening for receiving a dowel-like holder element or a clamping part with an inclined guide bore for a bone screw. For the guidance of the bone screws, which mainly serve to secure the anchoring part against rotation on a resection plane of the tibia, relatively voluminous bores are thus required for receiving the dowel and the clamping part, which can weaken the tibia bone. If for any reason, e.g. due to the state of the tibia bone tissue, the use of one or the other of the bone screws is dispensed with, abrasion of plastic and hence a direct contact between the plastic of the joint support and the tibia bone tissue may result--by cold flow of the plastic of the joint support in the region of the passage opening or passage openings not used in the particular case.